标题： 液滴撞击浅水池期间的涡环生成 显示英文标题

标题： Vortex ring generation during drop impact into a shallow pool

摘要： 当一个液滴从适中的高度落入一个浅层液体池中时，该液池的深度约为液滴半径的量级，会生成两对涡环。 内侧的一对涡环形成于撞击液滴所形成的凹坑边缘，而外侧的一对则由扩展波释放出来。 每一对涡环中有一个是短命的，另一个则持续存在。 每个涡环都有可测量的非零环流（尽管其符号与已知的深水液滴涡环的符号相反），这种环流在波浪退去后仍长时间存在。 此外，在某些条件下，它们会发展出典型的环涡不稳定性。 尽管这些涡环可以很好地重现，但它们后期的发展在某些实验参数发生变化时非常敏感。 本文报告了区分这些液滴生成涡环可重复性方面的实验，并记录了它们对材料和几何参数的依赖性。 显示英文摘要

摘要： When a drop falls from a moderate height into a shallow fluid pool whose depth is of the order of the drop-radius two pairs of vortex rings are generated. The inner pair forms at the edge of the crater created by the impacting drop while the outer pair is laid off from the spreading wave. One ring of each of these pairs is short-lived while the other persists. Each of the rings has a measureable non-zero circulation (whose sign, however, is opposite to that of the well-known deep-water drop vortex rings) which persists long after the wave has receded. Furthermore under certain conditions they develop instabilities typical to ring vortices. Although the rings are well reproducible, aspects of their later development are very sensitive to changes in some of the experimental parameters. This paper reports on experiments distinguishing reproducible aspects of these drop- generated rings and documenting their dependence on material and geometrical parameters.